The long-term objective of the body of research described in this application is to develop a unique technology for the transfer of cloned genes into the bovine germ line. In the long term, selection of genes to be introduced will be aimed at promoting animal longevity, disease resistance, accelerated growth parameters and increased nutrient utilization. The commercial application would be enormous. Existing technologies for the transfer of cloned genes into other types of embryo utilize nuclear microinjection, but that approach may be unacceptable for the embryos of agricultural animals due to technical problems. Instead, we propose to develop retroviral vectors for the infection of bovine embryos, a technique which will obviate the need for injection. The specific aims of this Phase 1 research proposal are: 1) to construct such vectors containing a model gene for feasibility studies; and 2) to test the infectivity and species specificity of such vectors in a tissue culture model system.